Do you think it would damage a four stroke engine to install a check valve in the breather line and then pressurize the fuel tank with it?

It would overpressurize the tank and when the tank pressure equalled the crankcase pressure oil would stop flowing out of the vent, you would then have an overabundance of oil and pressure in the crankcase reducing rpm and increasing the engine temperature. Plus, with that much pressure in the tank you would need a regulator to control the fuel flow.

I've see it done two ways. One is that you use muffler pressure with a check valve and the second method is to put a tee in the crankcase vent line. One outlet goes to a check valve and onto the tank and the other outlet just goes to the atmosphere through a nominal length of tube.

These two set ups only work when you use a Cline or Iron Bay type fuel regulator. Otherwise the pressure in the tank builds up too much to just run fuel straight to the needle valve. You will never get your mixture settings to settle down.


Enjoy,

Jim

Hi!
Why use it at all....???
Jan K

Huh? A 4 stroke crankcase pressurizes on the up stoke and pulls vacuum on the down stroke doesn't it? Whereas a 2 stroke pressurizes on the down stroke and is more neutral on the upstroke due to the intake (carb) port opening.

I don't see why you would want to use crankcase pressure (or try to) on a 4 stroke.

Ernie

You're joshing us aren't you Ernie?

There are allways vacuum in 2 stroke engine each time piston are raising from crankcase to combustion camber, if not the engine can not take fuel though carburator...

I has allways the tube from crankcase to out in free and not to connect to tank (some engine has tupe from crankcase to intake manifold).. There are dirt of old oil out of crankcase after the oil has cleaned and lubricated engine + remove crankcase gas from combustion. Can not understand why you will connect to tank when you has pressure from exhaustmuffler or use perry fuelpump...

Jens Eirik

I discovered there are a picture of the HP 4 stroke engine from Hirtenberger patronen...

Here are the pic how to connect the tubes without check valves..

Jens Eirik

I am looking to use a Cline regulator and didn't want to use muffler pressure this time.

My Saitos pressurize the tanks to the bulging point as does my Enya .53. on muffler pressure when using the Clines. Using the crankcase vent is a bad idea for several of the above mentioned reasons.